Context
Remote sensing has revolutionized oceanography, starting from sea surface temperature, ocean color, sea level, winds, waves, and the recent addition of sea surface salinity. Now the oceanographic community is at the doorstep of yet another revolution with the direct measurement of surface velocities related to currents, winds and waves. After demonstrations using pairs of interferometric synthetic aperture radars (InSAR) and the Doppler centroid from single SARs, Doppler Oceanography from Space has demonstrated its feasibility, and a global monitoring mission concepts, SKIM (Sea surface KInematics Multiscale monitoring: an ESA* satellite mission – https://www.skim-ee9.org/) is at detailed design and proposal stages for ESA and NASA**. It is also possible to use today’s SAR data for measuring a single component of this velocity vector.
Meeting
A meeting held in Brest, France, on October 10 to 12, 2018, gathered 100 international participants from academia, industry and space agencies. The event was technically co-sponsored by the IEEE Oceanic Engineering Society (OES) and with the support of ESA, CNES***, Brest Metropole (Sea Tech Week), IFREMER, IUEM****, Labex Mer***** and LOPS (Laboratoire d’Océanographie Physique et Spatiale). The workshop was organized around 24 oral presentations and 15 posters. It reviewed the gaps in the observation capabilities of currents, winds and waves, recent developments in radar technology, processing and the understanding of Doppler data. The meeting was recorded live on https://www.youtube.com/channel/UCG9o60slGCjji-jOFOngYgw or Facebook https://www.facebook.com/SKIM4EE9/.
Physical Oceanography Background

Gaps are particularly important for tropical currents, high latitudes, extreme winds, and high-resolution currents. Today’s tropical currents are estimated from near-surface drifters or the surface drift of Argo floats, with a very poor spatial coverage for the first (> 2000 km), and a very poor temporal coverage for the latter (30 minutes every week). Estimates of surface currents are otherwise made by combining satellite altimetry and wind from models or scatterometers. At the equator, even for time scales longer than 30 days, these estimates are very poorly correlated with drifter data (Sudre et al. 2013, see figure below for V component), so that we basically know better the winds on Mars than the surface currents at the equator of our own planet. This severely limits our understanding of the heat balance in the equatorial cold tongues and the forecasting capabilities of patterns such as the African monsoon.
At high latitude, sea ice is hiding most of the dynamics from the measurement capabilities of satellite altimeters, and where the sea ice is receding, the structures are too small to be resolved. Doppler radars can come in to measure near-ice current jets and the mesoscale of the emerging Arctic, which play a dominant role in defining the dynamics of the ice edge and transporting freshwater in the Arctic basin and around Greenland, both hugely important in global ocean circulation and its role in regulating the climate and weather.
Another area of great science and applications opportunities is opened when waves and currents, or winds and currents are measured simultaneously. This would allow a better understanding of extreme sea states and extreme waves, and a better understanding on the ocean energy cycle, from the wind-work to the energy cascade in the ocean circulation.
Technical Background
Most of these scientific requirements are easily achievable by recent technical developments in radar technology and our understanding or Doppler properties of radar backscatter from the ocean. Exploring ocean currents, winds and waves from space can now use mature Doppler radar technology, in particular SKIM will fill two important blind spots: in the tropics and in the marginal ice zone, and expand the effective space and time resolution of the altimeter constellation by a factor 2 or more. The novel direct measurement of surface currents in the top two meters will produce the first maps of the equatorial upwellings that are critical for understanding and forecasting the heat budget at the equator with far-reaching weather and climate consequences, for example on the African monsoon. OSCV (Ocean Surface Current Velocity) maps will also allow the first monitoring of the highly dynamic currents at the ice edge. Adding this new and fundamental variable to Earth Observation capability together with high fidelity measurements of wave spectra will allow scientists to address a wide range of questions, including:
- How OSCV and waves influence upper ocean mixing and large-scale circulation?
- How do OSCV and waves influence the dynamics of the ice edge in the Arctic and Antarctic?
- What are the roles of eddies, wind-driven flows and waves in setting the surface concentration of marine litter and shaping marine ecosystems?

Notes
*ESA: European Space Agency
**NASA: National Aeronautics and Space Administration
***Centre National d’Etudes Spatiales (the French Space Agency)
****IUEM: Institut Universitaire Européen de la Mer (part of the Brest University)
*****Labex Mer is a “Laboratory of Excellence” for the sea (la mer)


Dr. James V. Candy is the Chief Scientist for Engineering and former Director of the Center for Advanced Signal & Image Sciences at the University of California, Lawrence Livermore National Laboratory. Dr. Candy received a commission in the USAF in 1967 and was a Systems Engineer/Test Director from 1967 to 1971. He has been a Researcher at the Lawrence Livermore National Laboratory since 1976 holding various positions including that of Project Engineer for Signal Processing and Thrust Area Leader for Signal and Control Engineering. Educationally, he received his B.S.E.E. degree from the University of Cincinnati and his M.S.E. and Ph.D. degrees in Electrical Engineering from the University of Florida, Gainesville. He is a registered Control System Engineer in the state of California. He has been an Adjunct Professor at San Francisco State University, University of Santa Clara, and UC Berkeley, Extension teaching graduate courses in signal and image processing. He is an Adjunct Full-Professor at the University of California, Santa Barbara. Dr. Candy is a Fellow of the IEEE and a Fellow of the Acoustical Society of America (ASA) and elected as a Life Member (Fellow) at the University of Cambridge (Clare Hall College). He is a member of Eta Kappa Nu and Phi Kappa Phi honorary societies. He was elected as a Distinguished Alumnus by the University of Cincinnati. Dr. Candy received the IEEE Distinguished Technical Achievement Award for the “development of model-based signal processing in ocean acoustics.” Dr. Candy was selected as a IEEE Distinguished Lecturer for oceanic signal processing as well as presenting an IEEE tutorial on advanced signal processing available through their video website courses. He was nominated for the prestigious Edward Teller Fellowship at Lawrence Livermore National Laboratory. Dr. Candy was awarded the Interdisciplinary Helmholtz-Rayleigh Silver Medal in Signal Processing/Underwater Acoustics by the Acoustical Society of America for his technical contributions. He has published over 225 journal articles, book chapters, and technical reports as well as written three texts in signal processing, “Signal Processing: the Model-Based Approach,” (McGraw-Hill, 1986), “Signal Processing: the Modern Approach,” (McGraw-Hill, 1988), “Model-Based Signal Processing,” (Wiley/IEEE Press, 2006) and “Bayesian Signal Processing: Classical, Modern and Particle Filtering” (Wiley/IEEE Press, 2009). He was the General Chairman of the inaugural 2006 IEEE Nonlinear Statistical Signal Processing Workshop held at the Corpus Christi College, University of Cambridge. He has presented a variety of short courses and tutorials sponsored by the IEEE and ASA in Applied Signal Processing, Spectral Estimation, Advanced Digital Signal Processing, Applied Model-Based Signal Processing, Applied Acoustical Signal Processing, Model-Based Ocean Acoustic Signal Processing and Bayesian Signal Processing for IEEE Oceanic Engineering Society/ASA. He has also presented short courses in Applied Model-Based Signal Processing for the SPIE Optical Society. He is currently the IEEE Chair of the Technical Committee on “Sonar Signal and Image Processing” and was the Chair of the ASA Technical Committee on “Signal Processing in Acoustics” as well as being an Associate Editor for Signal Processing of ASA (on-line JASAXL). He was recently nominated for the Vice Presidency of the ASA and elected as a member of the Administrative Committee of IEEE OES. His research interests include Bayesian estimation, identification, spatial estimation, signal and image processing, array signal processing, nonlinear signal processing, tomography, sonar/radar processing and biomedical applications.
Kenneth Foote is a Senior Scientist at the Woods Hole Oceanographic Institution. He received a B.S. in Electrical Engineering from The George Washington University in 1968, and a Ph.D. in Physics from Brown University in 1973. He was an engineer at Raytheon Company, 1968-1974; postdoctoral scholar at Loughborough University of Technology, 1974-1975; research fellow and substitute lecturer at the University of Bergen, 1975-1981. He began working at the Institute of Marine Research, Bergen, in 1979; joined the Woods Hole Oceanographic Institution in 1999. His general area of expertise is in underwater sound scattering, with applications to the quantification of fish, other aquatic organisms, and physical scatterers in the water column and on the seafloor. In developing and transitioning acoustic methods and instruments to operations at sea, he has worked from 77°N to 55°S.
René Garello, professor at Télécom Bretagne, Fellow IEEE, co-leader of the TOMS (Traitements, Observations et Méthodes Statistiques) research team, in Pôle CID of the UMR CNRS 3192 Lab-STICC.
Professor Mal Heron is Adjunct Professor in the Marine Geophysical Laboratory at James Cook University in Townsville, Australia, and is CEO of Portmap Remote Ocean Sensing Pty Ltd. His PhD work in Auckland, New Zealand, was on radio-wave probing of the ionosphere, and that is reflected in his early ionospheric papers. He changed research fields to the scattering of HF radio waves from the ocean surface during the 1980s. Through the 1990s his research has broadened into oceanographic phenomena which can be studied by remote sensing, including HF radar and salinity mapping from airborne microwave radiometers . Throughout, there have been one-off papers where he has been involved in solving a problem in a cognate area like medical physics, and paleobiogeography. Occasionally, he has diverted into side-tracks like a burst of papers on the effect of bushfires on radio communications. His present project of the Australian Coastal Ocean Radar Network (ACORN) is about the development of new processing methods and applications of HF radar data to address oceanography problems. He is currently promoting the use of high resolution VHF ocean radars, based on the PortMap high resolution radar.
Hanu Singh graduated B.S. ECE and Computer Science (1989) from George Mason University and Ph.D. (1995) from MIT/Woods Hole.He led the development and commercialization of the Seabed AUV, nine of which are in operation at other universities and government laboratories around the world. He was technical lead for development and operations for Polar AUVs (Jaguar and Puma) and towed vehicles(Camper and Seasled), and the development and commercialization of the Jetyak ASVs, 18 of which are currently in use. He was involved in the development of UAS for polar and oceanographic applications, and high resolution multi-sensor acoustic and optical mapping with underwater vehicles on over 55 oceanographic cruises in support of physical oceanography, marine archaeology, biology, fisheries, coral reef studies, geology and geophysics and sea-ice studies. He is an accomplished Research Student advisor and has made strong collaborations across the US (including at MIT, SIO, Stanford, Columbia LDEO) and internationally including in the UK, Australia, Canada, Korea, Taiwan, China, Japan, India, Sweden and Norway. Hanu Singh is currently Chair of the IEEE Ocean Engineering Technology Committee on Autonomous Marine Systems with responsibilities that include organizing the biennial IEEE AUV Conference, 2008 onwards. Associate Editor, IEEE Journal of Oceanic Engineering, 2007-2011. Associate editor, Journal of Field Robotics 2012 onwards.
Milica Stojanovic graduated from the University of Belgrade, Serbia, in 1988, and received the M.S. and Ph.D. degrees in electrical engineering from Northeastern University in Boston, in 1991 and 1993. She was a Principal Scientist at the Massachusetts Institute of Technology, and in 2008 joined Northeastern University, where she is currently a Professor of electrical and computer engineering. She is also a Guest Investigator at the Woods Hole Oceanographic Institution. Milica’s research interests include digital communications theory, statistical signal processing and wireless networks, and their applications to underwater acoustic systems. She has made pioneering contributions to underwater acoustic communications, and her work has been widely cited. She is a Fellow of the IEEE, and serves as an Associate Editor for its Journal of Oceanic Engineering (and in the past for Transactions on Signal Processing and Transactions on Vehicular Technology). She also serves on the Advisory Board of the IEEE Communication Letters, and chairs the IEEE Ocean Engineering Society’s Technical Committee for Underwater Communication, Navigation and Positioning. Milica is the recipient of the 2015 IEEE/OES Distinguished Technical Achievement Award.
Dr. Paul C. Hines was born and raised in Glace Bay, Cape Breton. From 1977-1981 he attended Dalhousie University, Halifax, Nova Scotia, graduating with a B.Sc. (Hon) in Engineering-Physics.